Viewing file:  csum_partial_copy.c (3.42 KB) -rw-r--r--
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/*
* Network Checksum & Copy routine
*
* Copyright (C) 1999 Hewlett-Packard Co
* Copyright (C) 1999 Stephane Eranian <eranian@hpl.hp.com>
*
* Most of the code has been imported from Linux/Alpha
*/
#include <linux/types.h>
#include <linux/string.h>
#include <asm/uaccess.h>
/*
* XXX Fixme: those 2 inlines are meant for debugging and will go away
*/
static inline unsigned
short from64to16(unsigned long x)
{
/* add up 32-bit words for 33 bits */
x = (x & 0xffffffff) + (x >> 32);
/* add up 16-bit and 17-bit words for 17+c bits */
x = (x & 0xffff) + (x >> 16);
/* add up 16-bit and 2-bit for 16+c bit */
x = (x & 0xffff) + (x >> 16);
/* add up carry.. */
x = (x & 0xffff) + (x >> 16);
return x;
}
static inline
unsigned long do_csum_c(const unsigned char * buff, int len, unsigned int psum)
{
int odd, count;
unsigned long result = (unsigned long)psum;
if (len <= 0)
goto out;
odd = 1 & (unsigned long) buff;
if (odd) {
result = *buff << 8;
len--;
buff++;
}
count = len >> 1; /* nr of 16-bit words.. */
if (count) {
if (2 & (unsigned long) buff) {
result += *(unsigned short *) buff;
count--;
len -= 2;
buff += 2;
}
count >>= 1; /* nr of 32-bit words.. */
if (count) {
if (4 & (unsigned long) buff) {
result += *(unsigned int *) buff;
count--;
len -= 4;
buff += 4;
}
count >>= 1; /* nr of 64-bit words.. */
if (count) {
unsigned long carry = 0;
do {
unsigned long w = *(unsigned long *) buff;
count--;
buff += 8;
result += carry;
result += w;
carry = (w > result);
} while (count);
result += carry;
result = (result & 0xffffffff) + (result >> 32);
}
if (len & 4) {
result += *(unsigned int *) buff;
buff += 4;
}
}
if (len & 2) {
result += *(unsigned short *) buff;
buff += 2;
}
}
if (len & 1)
result += *buff;
result = from64to16(result);
if (odd)
result = ((result >> 8) & 0xff) | ((result & 0xff) << 8);
out:
return result;
}
/*
* XXX Fixme
*
* This is very ugly but temporary. THIS NEEDS SERIOUS ENHANCEMENTS.
* But it's very tricky to get right even in C.
*/
extern unsigned long do_csum(const unsigned char *, long);
static unsigned int
do_csum_partial_copy_from_user (const char *src, char *dst, int len,
unsigned int psum, int *errp)
{
unsigned long result;
/* XXX Fixme
* for now we separate the copy from checksum for obvious
* alignment difficulties. Look at the Alpha code and you'll be
* scared.
*/
if (__copy_from_user(dst, src, len) != 0 && errp)
*errp = -EFAULT;
result = do_csum(dst, len);
/* add in old sum, and carry.. */
result += psum;
/* 32+c bits -> 32 bits */
result = (result & 0xffffffff) + (result >> 32);
return result;
}
unsigned int
csum_partial_copy_from_user(const char *src, char *dst, int len,
unsigned int sum, int *errp)
{
if (!access_ok(src, len, VERIFY_READ)) {
*errp = -EFAULT;
memset(dst, 0, len);
return sum;
}
return do_csum_partial_copy_from_user(src, dst, len, sum, errp);
}
unsigned int
csum_partial_copy_nocheck(const char *src, char *dst, int len, unsigned int sum)
{
return do_csum_partial_copy_from_user(src, dst, len, sum, NULL);
}
unsigned int
csum_partial_copy (const char *src, char *dst, int len, unsigned int sum)
{
unsigned int ret;
int error = 0;
ret = do_csum_partial_copy_from_user(src, dst, len, sum, &error);
if (error)
printk("csum_partial_copy_old(): tell mingo to convert me!\n");
return ret;
}
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